Boron nitride (BN) is a most interesting III-IV compound from both the practical and scientific viewpoints. Boron nitride is characterized by three different crystal structures: hexagonal, wurtzite and cubic zincblende. The boron nitride phase having the cubic zincblende crystal structure is particularly useful since it is characterized by many desirable physical properties including high electrical resistivity and high thermal conductivity. In addition, the cubic zincblende boron nitride is relatively inert chemically. Because of these properties, this cubic form of the boron nitride is potentially very useful for electronic devices, particularly at high temperatures.
A cubic form of boron nitride has been grown on silicon wafers by means of a laser ablation technique, as disclosed in U.S. patent application Ser. No. 07/446,758 to Gary L. Doll et al, entitled "Laser Deposition of Crystalline Boron Nitride Films", filed on Dec. 6, 1989, and assigned to the same assignee of this patent application, now abandoned. With this laser ablation method, single crystal cubic boron nitride films were epitaxially grown on a silicon substrate oriented along the [100] axis, such that the resulting cubic boron nitride films were in epitaxial registry with the underlying silicon substrate.
As stated above, the cubic boron nitride has many characteristics useful for high temperature electronic applications However, it is necessary for the formation of electronic devices to have a silicon active layer. Therefore, it would be desirable to epitaxially grow a silicon layer over the cubic boron nitride which is in epitaxial registry with the underlying silicon substrate formed by the above laser ablation method. Such a silicon on boron nitride film would be a likely candidate for replacement of the silicon on sapphire systems which are currently in use for high temperature electronics.
The silicon on boron nitride system is advantageous in that the epitaxial interface between the overlaying silicon layer and boron nitride layer would be characterized by a clean lattice match between the two different materials' crystallographic structures, not like the mismatched lattices between the silicon and sapphire interface. This mismatch in lattice constants between the silicon and sapphire results in a drastic and non-reproducable shortening of the lifetime of the carrier in the silicon layer, thereby limiting the use of the silicon-on-sapphire transistors in high temperature devices.
It would therefore be desirable to provide a means for producing a device having an active silicon layer suitable for high temperature applications, such as an active silicon layer which is in epitaxial registry with an underlying cubic boron nitride film.